Television receiving and projecting means and method



June 4, 1935. DE FOREST v 2,003,530

TELEVISION RECEIVING AND PROJECTING MEANS AND METHOD Filed Sept. 22, 1931 h 27 ,9 7 firm INV ENTOR LEE or: Fewest ATTORNEY Patented June 4, 1935 PATENT OFFICE TELEVISION RECEIVDTG AND PROJECTING MEANS AND METHOD Lee de Forest, Hollywood, Calif., minor to American Television Laboratories, Inc., acorporation of Delaware Application September 22, 1931, Serial No. 664,331

60lalms.

This invention has to do in a general way with the art of forming pattern pictures or reproducing images in an opaque coating on a transparent or diaphanous base material such as film or the like.

More specifically, the invention has to do with improvements in the invention disclosed in my copending application Serial No. 532,454, filed April 24, 1931, in that it contemplates a novel type of film and the method of producing and using same for effecting the results contemplated in my former application.

My former application has to do with television receiving apparatus and'disclosesmeans for reproducing and projecting received I televised} ages. As pointed out'above, the'present'inv tion relates to improvements in apparatus of this character, and while the invention is described in connection with television receiving apparatus, it is to be understood that the invention is not necessarily confined to apparatus of this character, but may find various other applications in the reproduction of images to form pictures or in the formation of various designs and patterns.

The method described in my former application has to do with the formation of images upon a film or .suitable base member by electrically etching an opaque coating on the base member. sisted of ordinary motion picture film which had been uniformly exposed and developed to leave a deposit of silver in the gelatine on the so-called emulsion side of the film. treated in this manner was then passed between a stationary conducting plate and a revolving disk, the latter having provided upon its periphery a plurality of equally spaced discharge points. The discharge points of the disk energy which was modulated by received television signals coming from a television receiver. The disk was rotated at a' very high rate of speed, corresponding to the speed of a scanning disk at the television transmitter so that the film in passing thereunder was subjected to the action of electrical discharge from each point, the discharge correspondingin intensity to the light impressing the photoelectric cell at the transmitter, such light being received from the object or image being televised in any well known manner. Because of the high rate of speed of the moving discharge .there is practically no danger of igniting the film or base since the The type of film described therein con- The film,

discharge does not remain adjacent a given area of the film for a suflicient length of time to raise the temperature thereof appreciably.

In using the method and apparatus as disclosed in my co-pending application, I have found that the presence of an emulsion or gelatine in connection with the silver deposit on the coated surface of the film deters to a certain extent the etching or engraving action of the electrical discharge, thus impairing the sharpness of the image and having a deleterious effect upon the 'tone qualities of the finished picture.-

I have, therefore, conceived and developed a novel type of film which is particularly adapted, to1 thisj use in that the coating which is subjected" tothe action of the spark or discharge comprises a thin uniformly distributed layer of pure metal. The thickness of this layer is preferably of the order of several wave lengths of yellow light.

In using film of this nature with apparatus of discharge gap is completed without necessitating the discharge to take place through the film base.

The details in the construction of a preferred form of apparatus used in etching-or engraving film, together with a preferred process of coating the film, will be best understood from the following description of the accompanying drawing which is chosen for illustrative purposes only, and in which:

Fig. 1 is a plan view showing a preferred form of film coated in the manner contemplated by this invention; v

Fig. 2 is a plan view of the film etchingor engraving apparatus illustrating the manner in which a film is passed therethrough;

Fig. 3 is an enlarged sectional view whichmay be considered as having been taken along the line 3-3 in Fig. 2; and

Fig. 4 is an enlarged section showing the details in the construction of a preferred form of discharge gap.

Referring to the drawing, I have shown in Fig. 0

1 a section of film II which is of the type ordinarily used in connection with'motion pictures in that the edges of the film are provided with perforations l2 adapted to be engaged by suitable sprocket wheels such as are employed in the usual type of projecting apparatus. In this particular film the central portion between the perforations I2 is provided with a thin coating as indicated by reference numeral l3. This coating may be comprised of any suitable metal which can be unlformly applied, such as silver, magnesium, gold,

and the like, and as pointed out in the fore part of the specification, is of the order of several wave lengths of yellow light in thicknms. For my purpose the film H may be of any suitable transparent or diaphanous base material such as clear, uncoated celluloid film.

Although film of this character. may be coated in long lengths by various processes, I consider it preferable to coat the film by first cleaning the same in lye to remove all grease, then washing the film with tap water, thereafter scrubbing the surface of the film with a rotating scrubbing brush, after which it is passed through a bath of stannous chloride. The next step is to wash the film in tap water, followed by a thorough washing in distilled water, after which the film is passed through a silvering bath which may be of any one of several suitable solutions for depositing silver on organic surfaces. The silver deposited on the film by this first bath is extremely thin and the film is then washed in distilled water and may be passed through a second silvering bath similar to the first which materially increases the thickness of the silver deposit on the film. Although most of the silver has so' far been deposited on the cleaned surface of the film, it is important to remove any silver which has deposited on the opposite or celluloid side. For this purpose I pass the film again through a lye bath and over a scraper which removes any silver which may have been deposited on the reverse side of the film. This side of the film is then scrubbed by passing over a rotating scrubbing brush and is given a final washing in tap water. For this final washing step the film is passed directly through a dryer where it passes over a number of rolls in a chamber through which hot, dry air is circulating. When the film emerges from the drying cabinet it is rolled on reels holding 400 to 1000 feet, as the case may be, and is then ready to be used in the etching or engraving apparatus which will hereinafter he more fully described.

It is sometimes preferable to protect the newly applied metallic surface by applying a thin layer of transparent varnish or lacquer or a thin layer of amyl acetate thereto. Inasmuch as it is highly important to make as perfect a contact as'possible between the metalized surface and the point of contact in the electrical etching apparatus, I prefer to limit the area of metalized surface thus protected (when the entire surface of the film is coated with metal) to the area indicated at l3 in Fig. 1. In this manner the perforated margins of the film are provided with the metal coating but are not insulated in any way by the varnish or lacquer so that rollers or wiping brushes can make good contact with these uninsulated margins. If, on the other hand, I

do not choose to coat the metalized surfacewith a varnish, as pointed out above, I prefer to limit the coated area tothe portion indicated at l3. The object of so doing is to sharply limit the sparking action of the traveling discharge pointsto the area of film directly between the perforations. In producing a film with uncoated margins, as shown in the drawing, I may either coat the two margins with paraifin, molten wax, or the like, before thefilm passes through the silvering solution, or I may dip the margins. of the silvered film in a dilute solution of nitric. acid. Various other means for producing film.

with uncoated margins will no doubt appear to 5 those familiar with the art.

In Figs. 2 and 3 I show a preferred form of apparatus which may be used in etching or engraving film of the type described above. This apparatus consists in a general way of a disk 10 or rotatable plate l5 which is secured to a bearing hub l6 mounted upon a shaft II. The disk is provided near its periphery with a plurality of equally spaced discharge points 18' which may be of the type shown and described in my col5 pending application, or may be constructed as shown in Fig. 4 which will be described later in the specification, and each of these points is connected through an insulated conductor 18 to a segment 20 of a commutator H. The commu- 20 tator 2| has wiping contact with a brush 22 which is connected through a conductor 23 to a suitable source of electrical energy, not shown. The film Ii passes over a stationary plate or bridge 24 so that its coated surface is in close 25 proximity to the path traversed by the discharge points la. The coated surface of this film is engaged by a wiping brush or conducting roller 21 mounted between suitable resiliently controlled arms 28 and having electrical connection with a 30 cillations are modulated so as to vary the intensity of the electrical discharge. In the form of apparatus shown in my co-pending application which is used for reproducing televised images, modulations referred to are obtained from a television receiving circuit of any'standard type so that each discharge point as it rapidly swings transversely across the more slowly moving film is effective to perforate the film coating along a transverse line. This line, when viewed under the microscope, is shown to be .made up of a very large number of fine, individual perforations. The size of these perforations and the separation between the same depends upon the amount of electrical energy in the discharge between the point and the metalized surface, the distance of separation, the velocity of the moving part, and the condition of the air (temperature, degree of f ionization, etc.) in which the discharge takes place. It will be seen, therefore, that when the disk I5 has the same number of discharge points as the scanning disk of the television transmitter has perforations, and is rotating in synchro- L nism with the scanning. disk at the television transmitter, the intensity of the discharge of each point, as its corresponding commutator is engaged by the brush 22, will vary directly with Y the intensity of the light passing at that instant" through the corresponding. aperture in the scan-.- ning disk. In this manner the line traced by the discharge point varies in opacity with a corresponding line on the object or image which is viewed by the photoelectric cell associated with the transmitter scanning disk. Thus I am able to produce half tone pictures of the image at. the transmitting station in rapid succession and when such pictures are'produced onthe motion picture film as shown, they may be ims mediately projected through a projecting apparatus of the type shown in my co-pending application.

For the purpose of immediately removing from the spark gap all of the fine metal dust-which is released thereby, I may provide a blower 30 which is provided with a nozzle 3| positioned so as to direct a stream of air into the spark gap immediately above the film.

In Fig. 4 I show a preferred form of discharge point l8 which embodies a thick walled capillary tube of glass or other insulating material indicated at 35 mounted in the disk IS with its lower end at a distance of from .001 inch to .003 inch above the coated surface of the film H. The passage 36 through the capillary contains a conductor 31 which is cemented or otherwise secured therein with its lowermost end spaced above the lower end of the tube as shown. The distance between the lower end of the conductor 31 and the bottom of the capillary "may be varied over quite a wide range. I have obtained very good results with the lower end of the conductor spaced from .003 inch to .007 inch above the lower end of the capillary. In practice I have found that a discharge point of this nature produces a fine brush like discharge or spark which traces a fine line across the coated surface of the film, the line varying in density with the modulations in the current.

The pure metal coating, as described above, may be applied directly to the surface of an uncoated celluloid film or it may be applied upon a surface which has previously been coated with emulsion. It is an important feature, however, that the silver is not applied in conjunction with an emulsion or gelatine, but is in the nature of a pure metal surface which is extremely thin and is uniformly distributed.

It is to be understood that while I have described in the fore part of my specification a preferred method of applying this coating, other methods may be employed without changing the- .of suitable power mechanism and reduction gearing, all of which is preferably contained within the evacuated chamber. In passing between the two spools the film is drawn in close proximity to an electrically heated wire or ribbon composed of the metal (such as magnesium) to be deposited thereon. During this process extremely minute metallic particles are released or vaporized from the metal by the combined action of the heat and electrical repulsion in the vacuum and are deposited in a thin even layer upon that portion of the film which is passing adjacent to the disintegrating metallic body. In this case, as in the chemical deposition process, the thickness of the deposited metal layer can be gauged by controlling the speed at which the film is passed through the metalizing bath or solution. In the chemical process described above I prefer to pass the film through the bath and dryer at slow speed, preferably at from one to two feet per minute.

It is to be understood that while I have herein described certain preferred methods of treating or coating the film and have illustrated and described one preferred form of apparatus which may be used in etching or engraving the film, the invention is not limited to the precise details in these descriptions, but includes within its scope whatever changes fairly come within the spirit of the appended claims.

I claim as my invention:

1. For use in making television pictures, a transparent film having a continuous coating of substantially pure metallic silver applied to one surface thereof.

2. For use in apparatus for electrically etching a coated film: a rotatable disk; a plurality of angularly spaced capillary tubes mounted transversely in the periphery of said disk; a discharge conductor mounted in the passage through each of said tubes; a segmental commutator on said disk; conductors connecting each discharge conductor with one of the segments in said commutator; means for supporting a film below said disk; and means for connecting each segment with a source of potential as it traverses a film, said discharge conductors terminating above the lower ends of said capillary tubes.

3. In an apparatus of the class described,

means for etching a normally transparent film comprising a source of high frequency current having modulations corresponding to the etchingsv to be produced on said film, a rotatable capillary electrode carrier, said electrode terminating above the lower end of said capillary, means for applying said modulated currents to said coating and said electrode, and means for rotating said carrier and for moving said film in timed relation thereto.

4. For use in making television pictures, a transparent film having a continuous coating of substantially pure metal applied to the entire area of one surface thereof.

5. A moving picture film having a continuous coating of substantially pure metal applied to the entire area of one surface thereof.

6. A moving picture film having a continuous coating of substantially pure metal applied to the entire area of one surface thereof and a continuous coating of varnish over a central portion of said metallic coating.

- LEE or: FOREST, 

